Develop Reference

Check if webpage exists using Java

I'm using Java to check the response of a url I pass in. This is the current code I'm using. However, I keep getting a connection refused error. I'm testing with the basic Google home page so that I know the rough draft of my code works.
import java.io.BufferedReader;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.URL;
import javax.net.ssl.HttpsURLConnection;
public class connectTest {
public static void main(String[] args)
{
boolean test = pageExists();
}
public static boolean pageExists(){
int returnCode= 0;
try {
HttpURLConnection.setFollowRedirects(false);
String httpsURL = "https://www.google.com/";
URL testUrl = new URL(httpsURL);
HttpsURLConnection con =
(HttpsURLConnection)testUrl.openConnection();
returnCode= con.getResponseCode();
System.out.println(returnCode);
} catch (Exception e) {
e.printStackTrace();
}
if (returnCode== HttpURLConnection.HTTP_OK){
return true;
}
else if (returnCode== HttpURLConnection.HTTP_BAD_REQUEST || returnCode==
HttpURLConnection.HTTP_NOT_FOUND ){
return false;
}
else
{
System.out.println("The return code was not 200,400 or 404");
return false;
}
}
}
This is the error I get when I run the following:
java.net.ConnectException: Connection refused: connect
at java.net.DualStackPlainSocketImpl.connect0(Native Method)
at java.net.DualStackPlainSocketImpl.socketConnect(Unknown Source)
at java.net.AbstractPlainSocketImpl.doConnect(Unknown Source)
at java.net.AbstractPlainSocketImpl.connectToAddress(Unknown Source)
at java.net.AbstractPlainSocketImpl.connect(Unknown Source)
at java.net.PlainSocketImpl.connect(Unknown Source)
at java.net.SocksSocketImpl.connect(Unknown Source)
at java.net.Socket.connect(Unknown Source)
at sun.security.ssl.SSLSocketImpl.connect(Unknown Source)
at sun.security.ssl.BaseSSLSocketImpl.connect(Unknown Source)
at sun.net.NetworkClient.doConnect(Unknown Source)
at sun.net.www.http.HttpClient.openServer(Unknown Source)
at sun.net.www.http.HttpClient.openServer(Unknown Source)
at sun.net.www.protocol.https.HttpsClient.<init>(Unknown Source)
at sun.net.www.protocol.https.HttpsClient.New(Unknown Source)
at sun.net.www.protocol.https.AbstractDelegateHttpsURLConnection.getNewHttpClient(Unknown Source)
at sun.net.www.protocol.http.HttpURLConnection.plainConnect0(Unknown Source)
at sun.net.www.protocol.http.HttpURLConnection.plainConnect(Unknown Source)
at sun.net.www.protocol.https.AbstractDelegateHttpsURLConnection.connect(Unknown Source)
at sun.net.www.protocol.http.HttpURLConnection.getInputStream0(Unknown Source)
at sun.net.www.protocol.http.HttpURLConnection.getInputStream(Unknown Source)
at java.net.HttpURLConnection.getResponseCode(Unknown Source)
at sun.net.www.protocol.https.HttpsURLConnectionImpl.getResponseCode(Unknown Source)

java URL access I/O error

I am learning java. I've tried to access a website and see how many characters are there. A website I tried is:
http://cs.armstrong.edu/liang/data/Lincoln.txt
I get a I/O error: no such file output. but I shouldn't get since the web site is up & running.
package ikinciHaftam;
import java.io.IOException;
import java.net.MalformedURLException;
import java.net.URL;
import java.util.Scanner;
public class ReadFileFromURL {
public static void main(String[] args) {
// TODO Auto-generated method stub
System.out.print("Enter a URL: ");
Scanner inURL = new Scanner(System.in);
String URLString = inURL.next();
inURL.close();
try{
URL url = new URL(URLString);
int count =0;
Scanner input = new Scanner(url.openStream());
System.out.println(url.openStream());
while (input.hasNext()){
String line = input.nextLine();
count += line.length();
}
System.out.println("The file size is " + count + " characters");
input.close();
}
catch(MalformedURLException ex){
System.out.println("Malformed url");
}
catch(IOException e){
e.printStackTrace();
}
}
}
and I get:
java.net.UnknownHostException: cs.armstrong.edu
at java.net.AbstractPlainSocketImpl.connect(Unknown Source)
at java.net.PlainSocketImpl.connect(Unknown Source)
at java.net.SocksSocketImpl.connect(Unknown Source)
at java.net.Socket.connect(Unknown Source)
at java.net.Socket.connect(Unknown Source)
at sun.net.NetworkClient.doConnect(Unknown Source)
at sun.net.www.http.HttpClient.openServer(Unknown Source)
at sun.net.www.http.HttpClient.openServer(Unknown Source)
at sun.net.www.http.HttpClient.<init>(Unknown Source)
at sun.net.www.http.HttpClient.New(Unknown Source)
at sun.net.www.http.HttpClient.New(Unknown Source)
at sun.net.www.protocol.http.HttpURLConnection.getNewHttpClient(Unknown Source)
at sun.net.www.protocol.http.HttpURLConnection.plainConnect0(Unknown Source)
at sun.net.www.protocol.http.HttpURLConnection.plainConnect(Unknown Source)
at sun.net.www.protocol.http.HttpURLConnection.connect(Unknown Source)
at sun.net.www.protocol.http.HttpURLConnection.getInputStream0(Unknown Source)
at sun.net.www.protocol.http.HttpURLConnection.getInputStream(Unknown Source)
at java.net.URL.openStream(Unknown Source)
at ikinciHaftam.ReadFileFromURL.main(ReadFileFromURL.java:18)

FTPClient Connection refused

I am trying to copy file through FTPClient and testing in my local system
My code is like this with my IPv4 address as input for host
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import org.apache.commons.net.PrintCommandListener;
import org.apache.commons.net.ftp.FTP;
import org.apache.commons.net.ftp.FTPClient;
import org.apache.commons.net.ftp.FTPReply;
public class FTPUploader {
FTPClient ftp = null;
public FTPUploader(String host, String user, String pwd) throws Exception{
ftp = new FTPClient();
ftp.addProtocolCommandListener(new PrintCommandListener(new PrintWriter(System.out)));
int reply;
ftp.connect(host);
reply = ftp.getReplyCode();
if (!FTPReply.isPositiveCompletion(reply)) {
ftp.disconnect();
throw new Exception("Exception in connecting to FTP Server");
}
ftp.login(user, pwd);
ftp.setFileType(FTP.BINARY_FILE_TYPE);
ftp.enterLocalPassiveMode();
}
public void uploadFile(String localFileFullName, String fileName, String hostDir)
throws Exception {
try(InputStream input = new FileInputStream(new File(localFileFullName))){
this.ftp.storeFile(hostDir + fileName, input);
}
}
public void disconnect(){
if (this.ftp.isConnected()) {
try {
this.ftp.logout();
this.ftp.disconnect();
} catch (IOException f) {
// DO NOTHING
}
}
}
public static void main(String[] args) {
try{
System.out.println("Start");
FTPUploader ftpUploader = new FTPUploader("10.66.***.***", "username", "password");
ftpUploader.uploadFile("D:/Venkatesh.pptx", "65.pptx", "C:/Users/VENKATESH/Desktop");
ftpUploader.disconnect();
System.out.println("Done");
}catch(Exception exception){
exception.printStackTrace();
}
}
}
Now by this, Iam getting the following Exception
Start
java.net.ConnectException: Connection refused: connect
at java.net.DualStackPlainSocketImpl.connect0(Native Method)
at java.net.DualStackPlainSocketImpl.socketConnect(Unknown Source)
at java.net.AbstractPlainSocketImpl.doConnect(Unknown Source)
at java.net.AbstractPlainSocketImpl.connectToAddress(Unknown Source)
at java.net.AbstractPlainSocketImpl.connect(Unknown Source)
at java.net.PlainSocketImpl.connect(Unknown Source)
at java.net.SocksSocketImpl.connect(Unknown Source)
at java.net.Socket.connect(Unknown Source)
at org.apache.commons.net.SocketClient.connect(SocketClient.java:168)
at org.apache.commons.net.SocketClient.connect(SocketClient.java:189)
at org.apache.commons.net.SocketClient.connect(SocketClient.java:278)
at fileTransfer.FTPUploader.<init>(FTPUploader.java:21)
at fileTransfer.FTPUploader.main(FTPUploader.java:51)
What is the mistake iam doing ????

The program is absolutely fine.
Problem is at the server side.
Exception here is :
java.net.ConnectException: Connection refused: connect
at java.net.DualStackPlainSocketImpl.connect0(Native Method)
at java.net.DualStackPlainSocketImpl.socketConnect(Unknown Source)
at java.net.AbstractPlainSocketImpl.doConnect(Unknown Source)
at java.net.AbstractPlainSocketImpl.connectToAddress(Unknown Source)
at java.net.AbstractPlainSocketImpl.connect(Unknown Source)
at java.net.PlainSocketImpl.connect(Unknown Source)
at java.net.SocksSocketImpl.connect(Unknown Source)
at java.net.Socket.connect(Unknown Source)
The error is because of wrong credentials ( or ) the server is not started.
The file is transferred after restarting the server :)

I am trying to download facebook profile picture using java.But getting error

import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.Authenticator;
import java.net.PasswordAuthentication;
import java.net.URL;
public class SaveImageFromUrl {
public static void main(String[] args) throws Exception {
// proxy settings
System.setProperty("http.proxyHost", "porxyHost");
System.setProperty("http.proxyPort", "8080");
Authenticator authenticator = new Authenticator() {
public PasswordAuthentication getPasswordAuthentication() {
return (new PasswordAuthentication("userxyz","password".toCharArray()));
}
};
Authenticator.setDefault(authenticator);
String imageUrl = "https://graph.facebook.com/10000012233xxxx/picture";
String destinationFile = "D://image4.jpg";
saveImage(imageUrl, destinationFile);
}
public static void saveImage(String imageUrl, String destinationFile) throws IOException {
URL url = new URL(imageUrl);
InputStream is = url.openStream();
OutputStream os = new FileOutputStream(destinationFile);
byte[] b = new byte[2048];
int length;
while ((length = is.read(b)) != -1) {
os.write(b, 0, length);
}
is.close();
os.close();
}
}
My code works fine and downloads image for other imageurl paths.But it is not working when I use String imageUrl = "https://graph.facebook.com/10000012233xxxx/picture";
I am getting the following error :
Exception in thread "main" java.net.ConnectException: Connection timed out: connect
at java.net.DualStackPlainSocketImpl.connect0(Native Method)
at java.net.DualStackPlainSocketImpl.socketConnect(Unknown Source)
at java.net.AbstractPlainSocketImpl.doConnect(Unknown Source)
at java.net.AbstractPlainSocketImpl.connectToAddress(Unknown Source)
at java.net.AbstractPlainSocketImpl.connect(Unknown Source)
at java.net.PlainSocketImpl.connect(Unknown Source)
at java.net.SocksSocketImpl.connect(Unknown Source)
at java.net.Socket.connect(Unknown Source)
at sun.security.ssl.SSLSocketImpl.connect(Unknown Source)
at sun.security.ssl.BaseSSLSocketImpl.connect(Unknown Source)
at sun.net.NetworkClient.doConnect(Unknown Source)
at sun.net.www.http.HttpClient.openServer(Unknown Source)
at sun.net.www.http.HttpClient.openServer(Unknown Source)
at sun.net.www.protocol.https.HttpsClient.<init>(Unknown Source)
at sun.net.www.protocol.https.HttpsClient.New(Unknown Source)
at sun.net.www.protocol.https.AbstractDelegateHttpsURLConnection.getNewHttpClient(Unknown Source)
at sun.net.www.protocol.http.HttpURLConnection.plainConnect(Unknown Source)
at sun.net.www.protocol.https.AbstractDelegateHttpsURLConnection.connect(Unknown Source)
at sun.net.www.protocol.http.HttpURLConnection.getInputStream(Unknown Source)
at sun.net.www.protocol.https.HttpsURLConnectionImpl.getInputStream(Unknown Source)
at java.net.URL.openStream(Unknown Source)
at SaveImageFromUrl.saveImage(SaveImageFromUrl.java:33)
at SaveImageFromUrl.main(SaveImageFromUrl.java:28)

You need to make sure that your application can follow redirects, because Facebook is sending one if you request
/{user_id}/picture
To implement this, have a look at http://www.mkyong.com/java/java-httpurlconnection-follow-redirect-example/
Also, try setting the Proxy authentication like this:
System.setProperty( "http.proxyUserName", "username" );
System.setProperty( "http.proxyPassword", "password" );
I suspect you get the timeout from your proxy connection, but you should be able to test this yourself.

Couldnt able to connect REST api in java

I am trying to get response from below REST api. when I open that URL in browser, I gets xml repsonse from server. but when I am trying to get the same using java program I am getting below exception
IOEXCeption
java.net.UnknownHostException: rxnav.nlm.nih.gov
at java.net.AbstractPlainSocketImpl.connect(Unknown Source)
at java.net.PlainSocketImpl.connect(Unknown Source)
at java.net.SocksSocketImpl.connect(Unknown Source)
at java.net.Socket.connect(Unknown Source)
at java.net.Socket.connect(Unknown Source)
at sun.net.NetworkClient.doConnect(Unknown Source)
at sun.net.www.http.HttpClient.openServer(Unknown Source)
at sun.net.www.http.HttpClient.openServer(Unknown Source)
at sun.net.www.http.HttpClient.<init>(Unknown Source)
at sun.net.www.http.HttpClient.New(Unknown Source)
at sun.net.www.http.HttpClient.New(Unknown Source)
at sun.net.www.protocol.http.HttpURLConnection.getNewHttpClient(Unknown Source)
at sun.net.www.protocol.http.HttpURLConnection.plainConnect(Unknown Source)
at sun.net.www.protocol.http.HttpURLConnection.connect(Unknown Source)
at sun.net.www.protocol.http.HttpURLConnection.getInputStream(Unknown Source)
at java.net.HttpURLConnection.getResponseCode(Unknown Source)
at com.test.demo.RestConnector.run(RestConnector.java:22)
at java.lang.Thread.run(Unknown Source)
Pls help me regarding this
below is the code
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;
public class RestConnector implements Runnable{
#Override
public void run() {
String URLString = "http://rxnav.nlm.nih.gov/REST/classes?src=MESH";
try {
URL url = new URL(URLString);
HttpURLConnection connection = (HttpURLConnection)url.openConnection();
connection.setRequestMethod("GET");
connection.setRequestProperty("Accept", "application/xml");
if(connection.getResponseCode() != 200){
System.out.println("Failed to connect:"+connection.getResponseCode());
System.out.println("Response Message:"+connection.getResponseMessage());
}
System.out.println("I am here ");
BufferedReader reader = new BufferedReader(new InputStreamReader(connection.getInputStream()));
String line ;
while((line = reader.readLine()) != null){
System.out.println(line);
}
connection.disconnect();
} catch (MalformedURLException e) {
e.printStackTrace();
} catch (IOException e) {
System.out.println("IOEXCeption");
e.printStackTrace();
}
}
public static void main(String[] args) {
Thread t = new Thread(new RestConnector());
t.start();
}
}

1) The error clearly says "can't resolve hostname".
2) Q: Does your AndroidManifest.xml grant Internet permissions? Make sure it contains this line:
<uses-permission android:name="android.permission.INTERNET" />
3) Q: is this a real device, or an emulator? If the latter, consider recreating your AVD. Believe it or not, that can sometimes help: Android java.net.UnknownHostException: Host is unresolved.
4) Finally, here are some other tips - including proxy server configuration - that might help:
http://eliasbland.wordpress.com/2011/02/22/java-net-unknownhostexception-on-android-a-list-of-possible-causes/